This invention relates to expansion joints for bridges and other structures. DESCRIPTION OF RELATED ART
FIGS. 1A and 1 B respectively illustrate plan and elevation views of a conventional bridge 100. Bridge 100 consists of a main span 102 suspended by cables 104 between main towers 106 and 108. A side span 114 is suspended by cables 104 between main tower 106 and pier 116 while side span 118 is suspended by cables 104 between main tower 108 and pier 120.
Main span 102 is connected to main towers 106 and 108 by expansion joint assemblies 126 and 128, respectively. Side span 114 is connected to main tower 106 and pier 116 by expansion joint assemblies 130 and 132, respectively. Side span 118 is connected to main tower 108 and pier 120 by joint assemblies 134 and 136.
FIGS. 2A and 2B illustrate partial plan and elevation views of a bridge expansion joint assembly 200 that can be used for the expansion joint assemblies of bridge 100. Expansion joint assembly 200 includes an expansion joint 202 attached to a bridge superstructure (e.g., a deck on main tower 106) and an expansion joint 204 attached to another bridge superstructure (e.g., a deck on main span 102). Fingers 206 of expansion joint 202 are interdigitated with fingers 208 of expansion joint 204 over a sliding support 210 to accommodate relative motion along the longitudinal direction between main tower 106 and main span 102. Expansion joint assembly 200 allows bridge 100 to expand and contract with temperature changes.
Expansion joint assembly 200 does not accommodate vertical or transverse movement. Thus, expansion joint assembly 200 is ill suited for bridges in areas that have large magnitude earthquakes. Accordingly, what is needed is a multidirectional bridge deck expansion joint that will accommodate longitudinal, vertical, and transverse movement demands for new bridges and for seismic retrofitting of existing bridges to prevent serious bridge deck damage and possible loss of life resulting from large magnitude earthquakes.
In one embodiment of the invention, an expansion joint assembly includes a first expansion module and a second expansion module on opposing structures. The first expansion module includes a first hinge pivotally mounted to a first structure so the first hinge can rotate about a first axis, and a first group of fingers pivotally mounted to the first hinge so the first group of fingers can rotate about a second axis. The second expansion module includes a second hinge pivotally mounted to a second structure so the second hinge can rotate about a third axis, and a second group of fingers mounted, either fixedly or pivotally, to the second hinge. The first group of fingers and the second group of fingers are interdigitated and rest upon a sliding support.